External validation of the "optimal PSA follow-up schedule after radical prostatectomy” in a new cohort

Background: Biochemical recurrence (BCR) after radical prostatectomy (RP) is most commonly diagnosed by detecting an increase in asymptomatic prostate-specific antigen (PSA). We previously reported the “optimal PSA follow-up schedule after RP”. The aim of this study was to confirm the usefulness and safety of that follow-up schedule in another cohort. Methods: We retrospectively reviewed the clinicopathological data of 798 consecutive patients who underwent radical prostatectomy between 2009 and 2017. We examined all PSA values measured during follow-up. Furthermore, we estimated the PSA value when we observed the “optimal PSA follow-up schedule” at each timing in the virtual follow-up. BCR was defined as an elevation of PSA to greater than 0.2 ng/ml, and the ideal PSA range for detection of BCR was regarded to be 0.2–0.4 ng/ml. Results: During the mean follow-up period of 5.8 years, BCR occurred in 115 (14.9%) patients and the frequency of virtual follow-up was significantly lower than the actual frequency. However, overlooking of BCR (detecting BCR when PSA exceeded 0.4 ng/ml) was observed in 17 patients, which is higher than the actual frequency of overlooking (12 patients). Therefore, we modified the follow-up schedule, which could achieve the lower follow-up frequency and a limited number of overlooking of BCR (7 patients). Conclusion: This external validation study revealed that the "modified optimal PSA follow-up schedule after RP" can reduce the frequency of PSA measurement with a limited risk of overlooking BCR.